The present invention relates generally to ignition systems for automotive internal combustion engines, and specifically to a circuit arrangement for controlling the primary dwell time of an ignition transformer substantially at a constant value.
It is generally known in the art that in conventional ignition current control systems the primary dwell time of ignition transformer is detected and compared with a reference interval to detect the difference between them. The prior art systems include a negative feedback circuit which controls the duration of the ignition primary current so that the difference is reduced to a minimum. With the feedback operation the duration of the ignition primary current is substantially controlled to a desired constant value that ensures ignition at all engine speeds.
However, the amount of the output variable of the closed-loop system needs to be controlled to within a relatively narrow range to prevent undesirable effects of system's hunting and this in turn requires the system's component parts to be manufactured to strict tolerances and adjusted constantly during operation to keep them in specified operating conditions.